crankshaft
Enable an AI agent to recognise a crankshaft, assess its condition and compatibility, and determine which installation, inspection, operation or repair actions its evidence supports.
Research draft, second pass
A second pass drafted this model: the structure a model of this thing needs, and what is known about it in the world. The line under this one says how the second half was obtained - researched against sources, or recalled without web access, in which case nothing here was read anywhere and every claim is a lead to verify. Unreviewed either way.
Researched by: Codex + Grok
Purpose and description
Enable an AI agent to recognise a crankshaft, assess its condition and compatibility, and determine which installation, inspection, operation or repair actions its evidence supports.
A crankshaft is a rotating machine element that converts the reciprocating linear motion of pistons into rotary motion (or the reverse) through offset crank throws connected by crankpins, with main journals that run in bearings in the engine or machine frame.
It can be Identify the crankshaft and compare its throw arrangement and interfaces with a proposed application.; Plan and record journal, runout, surface and structural inspections against applicable criteria.; Verify crankshaft lubrication passages and plugs where fitted.; Assess bearing-size selection, axial location and mating-component compatibility before installation.; Evaluate proposed grinding, polishing, straightening or built-up alignment work against documented permissions and limits.; Recommend installation, continued service, further inspection or retirement with explicit evidence and unresolved conditions..
Distinguishing features
Identify a supported main rotation axis and at least one crankpin axis offset from it; an ordinary straight transmission shaft lacks this crank arrangement.
Establish that the offset journal interfaces with a connecting rod or equivalent link to couple rotation and reciprocation; a camshaft instead uses a cam profile to govern follower motion.
Trace the structural connection from crankpin through webs or equivalent members to the main-axis shaft portions; an eccentric sleeve alone does not establish a complete crankshaft.
Check the component boundary against drawings or assembly records: a crankshaft may be built from joined parts, so visible joints do not by themselves disqualify it.
Distinguish the shaft component from a separate crank arm, crank disc or eccentric attachment by locating its main-bearing support surfaces and assembly boundary.
Scope
+ Main journals, offset crankpins, crank throws, webs and integral counterweights
+ Component identity, configuration and application compatibility
+ Journal geometry, alignment, surface condition and structural integrity
+ Integral lubrication passages and interfaces for bearings, connecting rods, seals and attached equipment
+ Evidence supporting installation, continued service, reconditioning or retirement
- Complete engine, compressor or pump performance and operating control
- Connecting-rod, piston and cylinder condition beyond their crankshaft interfaces
- Bearing-shell design and lubrication-system performance beyond crankshaft requirements
- Flywheel, damper, pulley and coupling internals
- Detailed machining equipment, inspection-instrument and workshop-process models
Characteristics
- Component identity and revision
- Manufacturer, part number, revision, serial or traceability marking; unknown where unverified Similar-looking crankshafts can have different fit, balance and service requirements.
- Construction
- One-piece, built-up or other documented construction; material and treatment designation where verified Construction affects inspection, alignment assessment and permissible repair.
- Crank throw geometry
- Crankpin count; offset from main axis in mm; axial positions in mm; relative angular positions in degrees The arrangement determines the motion geometry and compatibility with the intended mechanism.
- Journal dimensions and form
- Main-journal and crankpin diameters and widths in mm; taper and out-of-round in µm or mm, with measurement locations Bearing fit and reconditioning decisions depend on local geometry rather than a nominal diameter alone.
- Axis alignment and runout
- µm or mm at stated surfaces, with datum, support arrangement and measurement method A runout value is interpretable only with its setup and applicable acceptance limit.
- Journal and transition condition
- Observed wear, scoring, corrosion, heat discoloration, crack indications or no relevant indications under a stated inspection Surface and structural evidence constrain whether the crankshaft can remain in service.
- Lubrication-path condition
- Passage configuration documented, clear, obstructed, damaged, unverified or not applicable Where internal oil paths exist, their condition affects oil delivery through the crankshaft.
- Mating-component compatibility
- Links to approved bearings, connecting rods, housing, seals, flywheel, damper and drive components as applicable Physical fit alone does not establish an approved or serviceable assembly.
- Balance configuration
- Counterweight arrangement, required external balance components and applicable balance specification Balance evidence must correspond to the intended rotating and reciprocating assembly.
- Service and reconditioning status
- Unassessed, accepted for stated application, restricted, awaiting approved repair or rejected; supporting authority and evidence The agent needs a justified disposition that distinguishes missing evidence from demonstrated failure.
Where this came from
wikidata · CC0 1.0
Drafted structure
Bundle to layer to finding to question, as the second pass will find it: 6 bundles · 11 layers · 18 findings · 28 questions.
Identity and crank geometry Establish which component this is and how its supported axis and offset journals form a crankshaft.
Recognition and application matching require the actual crank arrangement and component boundary.
Component identity
Identify the crankshaft variant and distinguish integral features from separate assembly members.
Traceable crankshaft variant
Record markings and documentary evidence for identity, revision and one-piece or built-up construction without inferring them from appearance alone.
- Which markings, drawings or manufacturer records identify this crankshaft and its revision? provenance
- Which webs, counterweights, gears or end fittings belong to this component, and which are separately replaceable parts? boundary
Throw arrangement
Describe the main axis, crankpin offsets and relative throw positions.
Main axis and offset journals
Record the journal layout that couples shaft rotation to connecting-link motion.
- Which surfaces establish the main rotation axis, and which journals serve as offset crankpins? definition
- What are the crankpin offsets, axial positions and relative angles, and how were they established? measurement
Bearing and drive interfaces Describe the surfaces and connections through which the crankshaft is supported, located and coupled to other parts.
Correct crank geometry does not establish bearing fit, axial control or compatibility with attached equipment.
Journal and thrust fit
Capture the geometry needed to assess main-bearing, connecting-rod-bearing and thrust interfaces.
Bearing fit evidence
Record journal size, form, transitions and thrust surfaces against the intended mating parts.
- What are each journal's measured diameter, width, taper and out-of-round, including any documented undersize designation? measurement
- Which bearing and thrust arrangements are approved, and what assembly measurements are still needed to establish clearance and end float? boundary
Shaft-end connections
Identify torque-transfer, timing-location and sealing interfaces where present.
End-interface compatibility
Record flange, nose, keyway, spline, thread and seal-track features relevant to the actual variant.
- Which end-interface dimensions, locating features and seal surfaces must match the intended attached components? measurement
- Which installation specifications govern orientation, fastening and permissible restoration of these interfaces? action
Lubrication and working surfaces Assess journal surfaces and any internal oil routes serving crankshaft bearing interfaces.
A dimensionally compatible crankshaft can still have damaged running surfaces or compromised oil paths.
Internal oil routing
Establish whether internal lubrication passages exist and assess their configuration and condition.
Oil-path continuity
Record passage routing, openings and plugs where fitted, together with evidence of cleanliness and integrity.
- Does this design route lubricant through the crankshaft, and which inlets, outlets and plugs form each documented path? definition
- What approved cleaning and verification actions establish passage condition and plug security after service or machining? action
Journal surface quality
Assess running surfaces, oil-hole edges and adjacent transitions.
Surface serviceability
Record roughness and local damage with enough location detail to judge bearing-interface serviceability.
- What surface-finish measurements and observations of scoring, pitting or other damage exist for each journal? measurement
- Which applicable criteria govern journal finish, oil-hole edge treatment and whether polishing or grinding is permitted? action
Structural and dynamic condition Assess crankshaft integrity, alignment and balance in the relevant assembly configuration.
Local journal measurements alone cannot establish freedom from structural damage or suitability for the intended dynamic loading.
Integrity and alignment
Capture evidence concerning cracks, distortion and joined-member movement.
Structural inspection evidence
Keep inspection indications and alignment results distinct from their acceptance decision.
- Which inspection methods covered the journals, fillets, webs and joints as applicable, and what indications or coverage limitations were recorded? provenance
- What runout or built-up alignment measurements were obtained, using which datums and supports, and against which limits? measurement
Balance and torsional context
Relate counterweights and attached rotating components to applicable balance and torsional requirements.
Validated rotating configuration
Associate balance evidence and operating restrictions with the exact configuration they cover.
- Which counterweights, external balance components and representative reciprocating masses were assumed in the applicable balance specification or test? provenance
- Which speed, load or torsional restrictions apply to this crankshaft configuration, and which depend on the surrounding machine and damper? boundary
Service history and disposition Connect manufacturing and service evidence to permissible reconditioning and a justified next action.
Crankshaft treatments and prior repairs can constrain subsequent machining and service decisions even when current dimensions appear acceptable.
Material, treatment and history
Establish evidence for material condition, manufacturing treatments and previous interventions.
Reconditioning constraints
Record verified material and treatment information alongside prior grinding, straightening, joint adjustment or other repairs.
- What records establish the material, hardening or surface treatment, and any treatment of journal fillets? provenance
- What previous repairs or damage events are documented, and how do applicable instructions constrain further material removal or alignment work? action
Acceptance and next action
Determine a disposition for a stated application from inspection evidence and applicable instructions.
Evidence-backed disposition
Separate accepted, repairable, rejected and unresolved conditions, preserving the basis and scope of the decision.
- Which authoritative acceptance criteria and completed inspections support the proposed disposition for this application? provenance
- What must happen next - installation checks, further inspection, approved reconditioning or retirement - and what evidence is required before release? action
Evidence and external alignment What the world already says about this thing, gathered so the model can be checked against it.
A model that cannot be lined up against existing standards, identifiers and practice cannot be adopted by anyone who already uses them.
Reported evidence
Findings from the breadth pass, kept separate from the structural claims.
Kinds and varieties
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- Inline / straight crankshaft (throws in one plane for inline engines)
- V-engine crankshaft (throws arranged at the V-angle, typically 60° or 90°)
- Boxer / opposed-piston crankshaft (throws 180° apart)
- Radial-engine crankshaft (master-and-articulating-rod arrangement, often single-throw or two-throw)
- Forged steel crankshaft
- Cast iron / nodular-iron crankshaft
- Billet / machined crankshaft
- Assembled / built-up crankshaft (pressed or bolted throws, common in large two-stroke diesels and some small engines)
- Which of these kinds and varieties hold for the sense of crankshaft this model covers, and on what evidence? provenance
Identifiers and schemes
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- Wikidata - Q5349 - item 'crankshaft'
- Which of these identifiers and schemes hold for the sense of crankshaft this model covers, and on what evidence? provenance
Standards and regulation
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- ISO 6621 / related piston-engine component families (ISO) - dimensional and material practice around reciprocating engines (crankshafts themselves are more often specified in OEM and classification-society rules than in a single ISO product standard)
- IACS UR M53 / classification-society crankshaft fatigue rules (IACS, with implementations by DNV, ABS, Lloyd's Register, etc.) - marine diesel crankshaft scantlings and fatigue assessment
- SAE J1999 / SAE engine-component material and fatigue practice (SAE International) - automotive crankshaft material and testing context
- DIN 743 (shaft calculation) and related national shaft-design codes - used for general machine crankshafts outside automotive OEM specs
- Which of these standards and regulation hold for the sense of crankshaft this model covers, and on what evidence? provenance
Real-world use
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- Internal-combustion engine of cars, trucks, motorcycles, ships, locomotives, and aircraft, converting piston strokes into flywheel/output-shaft rotation
- Reciprocating compressors and pumps, converting rotary drive into piston motion
- Steam engines and some Stirling engines, same kinematic role
- Presses, punches, and mechanical shears that use a crank to produce a working stroke
- Which of these real-world use hold for the sense of crankshaft this model covers, and on what evidence? provenance
Typical measurements
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- Main-journal diameter - 30-150 (automotive); 200-800 (large marine) - mm
- Stroke (twice crank throw radius) - 70-110 (passenger car); 200-350 (heavy truck); 1000-3500 (large two-stroke marine) - mm
- Number of throws / cylinders served - 1-16 (common production); up to ~20 in some large engines - count
- Mass - 10-40 (passenger car); 50-200 (truck); several tonnes (marine) - kg
- Tensile / yield strength of material - 700-1200 (forged steel); 500-800 (nodular iron) - MPa
- Fillet radius at journal-web junction - 1-6 (small engines, often rolled); larger and often undercut or ground on heavy shafts - mm
- Which of these typical measurements hold for the sense of crankshaft this model covers, and on what evidence? provenance
Failure modes and hazards
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- Fatigue fracture initiating at crankpin or main-journal fillets, oil holes, or web-to-journal transitions under cyclic bending and torsion
- Journal wear, scoring, or bearing wipe from oil starvation, contamination, or misalignment
- Twisting or bending from overload, hydrolock, or detonation, producing runout and subsequent bearing failure
- Fretting or loosening of press-fit counterweights or assembled-throw joints
- If the shaft fails in service: sudden loss of drive, thrown fragments, oil fire risk in engines, and in marine/industrial plants possible uncontrolled stop of a critical machine
- Which of these failure modes and hazards hold for the sense of crankshaft this model covers, and on what evidence? provenance
Regional variation
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- English: crankshaft; German: Kurbelwelle; French: vilebrequin; Italian: albero a gomiti / albero motore; Japanese: クランクシャフト (kurankushafuto) or クランク軸
- Large two-stroke marine practice (assembled, fully built-up or semi-built shafts, classification-society approval) differs sharply from automotive one-piece forged or cast shafts
- US automotive aftermarket often classes shafts as cast, forged, or billet; European OEM literature more often specifies the steel grade and the manufacturing route (die-forged, cast GJS, etc.)
- Which of these regional variation hold for the sense of crankshaft this model covers, and on what evidence? provenance
Neighbouring kinds and how to tell them apart
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- Camshaft - A camshaft times valve events via cams; a crankshaft takes piston force via connecting rods. Test: presence of crank throws and rod journals versus cam lobes.
- Crank (simple crank or crank arm) - A simple crank is a single offset arm; a crankshaft is a shaft with one or more throws, usually with main journals at both ends. Test: multiple main bearings and/or multiple throws on one axis.
- Connecting rod - The rod links piston to crankpin and articulates; it does not rotate continuously as the output member. Test: big-end bearing on a crankpin versus a rotating shaft with journals.
- Flywheel - The flywheel stores rotational energy and is usually bolted to a crankshaft flange; it is not the converting element. Test: mass of revolution without throws versus a shaft with crankpins.
- Eccentric shaft - An eccentric has a circular offset journal whose centre is displaced but still a full circle (Wankel, some pumps); a crank throw is a pin between webs. Test: full-diameter eccentric versus a pin of smaller diameter between cheeks.
- Which of these neighbouring kinds and how to tell them apart hold for the sense of crankshaft this model covers, and on what evidence? provenance
Sources
- Crankshaft - Definition, kinds, neighbours, history, and typical engine applications.
What the second pass must settle
- Does the registry intend crankshaft to include all built-up and single-throw forms, and where should it draw the boundary with crank axles and eccentric shafts?
- Which manufacturer or application-specific sources should govern journal tolerances, runout, surface finish and structural acceptance for each supported variant?
- How should the model represent permitted reconditioning when material, hardening depth, fillet treatment or previous machining history cannot be verified?
- Which balance and torsional requirements belong directly to a crankshaft variant, and which must remain decisions of the complete machine model?
- What minimum inspection coverage and traceability are required to move a crankshaft from unassessed to accepted for a stated application?